A class contains reference to Application and View which are needed by external command.
Namespace: Autodesk.Revit.UI
Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 24.0.0.0 (24.0.0.0)
Namespace: Autodesk.Revit.UI
Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 24.0.0.0 (24.0.0.0)